Pros
Clear-cut training, low-commitment work, small company that might provide the opportunity for career growth if you're willing to work for it. I was offered a full-time position within the window of my 3 month contract to hire, so if you really stand out (and I mean *really* stand out), you'll probably move up the ladder quickly. $0.75 shift differential if you're willing to work 2nd shift (maybe that's a pro for some people?).
Cons
Highly repetitive work, and (it seems) the company thinks too highly of itself, which is most apparent in the advanced backgrounds they want for low-level workers (see example below).
When I hired on through a contract agency, the preferred experience was listed as "4 year bio-related degree with industry experience" and the required experience (which I found out later) is a "high school degree and attention to detail." Nowhere else have I ever seen such a far jump between those two sets of experience. As a former biologist with a Fortune 500 company, I honestly don't know why I was considered for the position. I value an honest day's work and don't expect promotions to be handed to me, but if they wanted to keep me, they should have brought me in at a higher level where my talents would have been used.